ClickHouse/dbms/src/IO/ReadBufferFromMemory.cpp

#include "ReadBufferFromMemory.h"

namespace DB
{

namespace ErrorCodes
{
	extern const int CANNOT_SEEK_THROUGH_FILE;
	extern const int SEEK_POSITION_OUT_OF_BOUND;
}

off_t ReadBufferFromMemory::seek(off_t offset, int whence)
{
	if (whence == SEEK_SET)
	{
		if (offset >= 0 && working_buffer.begin() + offset < working_buffer.end())
		{
			pos = working_buffer.begin() + offset;
			return size_t(pos - working_buffer.begin());
		}
		else
			throw Exception("Seek position is out of bounds. "
				   "Offset: " + std::to_string(offset) +
				   ", Max: " + std::to_string(size_t(working_buffer.end() - working_buffer.begin())),
				   ErrorCodes::SEEK_POSITION_OUT_OF_BOUND);
	}
	else if (whence == SEEK_CUR)
	{
		Position new_pos = pos + offset;
		if (new_pos >= working_buffer.begin() && new_pos < working_buffer.end())
		{
			pos = new_pos;
			return size_t(pos - working_buffer.begin());
		}
		else
			throw Exception("Seek position is out of bounds. "
				  "Offset: " + std::to_string(offset) +
				  ", Max: " + std::to_string(size_t(working_buffer.end() - working_buffer.begin())),
				  ErrorCodes::SEEK_POSITION_OUT_OF_BOUND);
	}
	else
		throw Exception("Only SEEK_SET and SEEK_CUR seek modes allowed.", ErrorCodes::CANNOT_SEEK_THROUGH_FILE);
}

}